Research On Nonlinear Dynamics Of The Rotating Blade Of Horizontal Axis Wind Turbine

It is known to us that the energy is very important for the living and development of the human society. To view on the current situation, the entire world is facing with the problem of energy drying up and irrational energy structure. On the one hand, many countries have made the completion all around the world to seek the energy. On the other hand, the polluted energy has led to serious negative effect to the global environment. Now people are starving for the energy which is clean and has big storage. The recycled energy is attracting more and more people's attention. As the limitation of the conventional energy, the instability of its supply, and the environment pollution, the development and utilization of wind energy, which has little affection to the environment, is becoming more and more popular around the word after 1970.The wind turbine has a very important position to the utilization of wind energy, and wind turbine blade is one of the most important components. The blade is long span, short chord, and the load on the blade is more complicated, as the aerodynamic forces, elastic forces and inertia forces are applied on the blade. The vibration of the blade may cause big damage.In this thesis, the nonlinear dynamics of the rotating blade of horizontal axis wind turbine has been investigated, considering the forces caused by the pulse wind. The main content of the thesis consists of the following parts.(1) The blade of horizontal axis wind turbine is modeled as a rotating cantilever beam. The nonlinear governing equation of motion for the rotating cantilevered blade with harmonic wind forces is obtained based on the Newton's law of motion.(2) Considering the quadratic term, the method of Asymptotic Perturbation is employed to transform the governing equation of motion to the averaged equations in the case of 1/2 subharmonic resonance and 1:3 internal resonance. The planar phase portrait, three-dimensional phase portrait, waveform and frequency spectrum of the averaged equations are obtained by using numerical simulation. The influence of the mean wind speed and stochastic wind speed on the system is studied.(3) The case of 1/2 subharmonic resonance and 1:2 internal resonance is considered. Numerical simulation is used to get the three-dimensional phase portrait, waveform and frequency spectrum of the averaged equations to investigate the wind velocity on the system.(4) The results of numerical simulation indicate that there exist the periodic, periodic-n, quasi-periodic and chaotic motions for rotating blade of horizontal axis wind turbine in both of the two resonant cases. By changing the wind velocity or the stochastic angular speed in numerical simulation, the procedure of motions of the system is periodic→chaotic→periodic.